Refining mineral oil



Dec. 1, 1959 l. w. MILLS ETAL 2,915,460

REFINING MINERAL OIL Filed Dec. 30, 1954 O Bauxite Containing I IronCompound l0 Sour Gasoline Aqueous NHOH Ammonia Treatment I I2 SweeteningDrying J Sweetened Gasoline Bauxite 2o Magnetic Separation Sour Gasoline2| 23 Aqueous NGOH Caustic Treatment sweetening Water Wash 22 DryingSweetened Gasoline INVENTORS. IVOR W. MILLS BY PETER B. MURRAY Wkzb$(wli1 ATTOR NE Y United States Patent 2,915,460 REFINING MiNERAL OILIvor W. Mills, Glenolden, and Peter B. Murray, Media, Pa., assignors toSun Oil Company, Philadelphia, Pa., a

corporation of New Jersey 1 Application December 30, 1954, Serial No.478,768 Claims; (Cl. 208-489) This invention mates; to the refining ofmineral oil and more particularly to the conversion or removal ofmercaptans and other objectionable sulfur compounds from mineral oil.

Various means have been proposed for converting or removing mercaptansfrom various mineral oilfractions such as gasoline, naphtha, etc., andsome of the means which have been proposed may produce a product havity, the mineral oil products obtainedsubsequently from that bauxitewill contain unsatisfactorily large amounts of mercaptans.

According to the invention, a process for reduction of mercaptancontent, employing an adsorbent, is provided wherein the life of theadsorbent is substantially increased. This makes it possibleto treatmineral oil, for substantially longer periods before having toregenerate or discard the adsorbent.

The process of the invention is applicable to those adsorbents whichcontain' iron or iron compounds. The process of the invention involvesthe treatment of the adsorbent with an alkali prior to the use of theadsorbent as a-sweetening agent for mineral oili Alkalis, for thepurpose of the present invention, are considered to include ammonia,-ammonium hydroxide, ammonium carbonate, and'the alkali metal hydroxidesand carbonates, e.g. sodium hydroxide, sodium carbonate, potassiumhydroxide, potassium carbonate, etc. Generally; aqueous solutions ofalkalis will be employed in treating adsorbents according to theinvention, but gaseous ammonia can also be employed.

It has been found'that treatment of adsorbents, with alkalis assubsequently more fully described, considerably increases the-ability ofthe adsorbent to reduce the mercaptan content of hydrocarbon materials.

The invention will be further described with reference to the attacheddrawings. Figure 1 is aschematic flow sheet of one embodiment of theproce'ssaccording to the invention. Figure 2 is a schematic flow sheetof another embodiment.

Referring to Figure 1, bauxite containing iron compounds is introducedinto ammonia treating zone 10. The bauxite which is introduced may be abauxite which has not been givenany prior treatment other than thecustomary thermal= activation, eg at a temperature of 600700 F. orhigher, and which contains substantial amounts of iron oxide, generallywithin the range from 1 ton25 percent,.for exampleabout 15 percent;other iron compounds may also'be present. Alternatively'the V 2 bauxiteintroduced into zone 10 may have been treated in any known manner toreduce the iron content. It is to be noted however that preferably theiron content of the bauxite employed is high, and therefore it is notpreferred to use a bauxite which has been treated for reduction of ironcontent.

The bauxite introduced in zone 10 may have been treated beforehand toincrease the iron content, for example by contacting the bauxite with anaqueous solution of an iron salt, eg ferrous or ferric chloride,sulfate, acetate, etc., preferably though not necessarily having atleast 10 weight percent concentration, followed by evaporation of waterfrom the impregnated bauxite.

Aqueous ammonium hydroxide is introduced into zone 10 and is contactedtherein-with the bauxite. The contacting may be accomplished forexampleby percolating an aqueous solution of ammonium hydroxide through astationary bed of'granular bauxite. The bauxite is subsequently dried inany suitable manner, as indicated by the drying zone 11. In practice itis not necessary .to transfer the bauxite from one zone to another asindicated in the drawing. Instead-a stationary bed of bauxite which hasbeen treated with ammonium hydroxide may be subsequently dried byblowing heated gases, e.g. air, through the bed of bauxite.

In the drying operation excess water is removed from the bauxite, andalso excess ammonia is removed. It is not essential to this embodimentof the process of the invention that ammonia be present during thesweetening operation. It appears rather that-the ammonia merely has theefiect of converting the ironin the adsorbent to a different andsuperior form.

The conditions employed in the drying operation generally involve theuse of a temperature within the approximate range from 150 F. to 600 F.,preferably 200 F. to 400 F, for a suflicient period of time to obtainequilibrium at the temperature employed; the temperature employed shouldbe above the boiling point of water at the pressure employed. The dryingcan for example be performed at atmospheric pressure or under vacuumconditions, e.g. at an absolute pressure less than about mm. Hg. Thewater removed by such drying is mainly or entirely of the type generallyknown as free moisture, rather than. the combined water which may beremoved upon ignition of the bauxite.

Sour gasoline containing mercaptans or other objectionable sulfurcompounds is sweetened by contact With' the bauxite which has beentreated with ammonia and dried; the sweetening operation is indicated atzone 12. Here again it is not necessary to transfer the bauxite from onezone to another; instead the gasoline can be percolated through the samestationary bed of bauxite, after the termination of the dryingoperation.

Preferred conditions for the sweetening operation involve the use ofatmospheric temperature and pressure. Elevated temperatures can beemployed if desired, for example up to 250 F. However such elevatedtemperatures are notnecessary for etficient reduction of mercaptancontent, and may have an adverse effect upon the gum rating of theproduct obtained in the sweetening operation, particularly in the caseof a cracked charge stock.

It is believed that the process of the invention involves not merelyphysical adsorption of constituents of the charge on the adsorbent, butan oxidation of mercaptan constituents, and that the presence of oxygenis therefore required during the contact of adsorbent with hydrocarbon:material. Frequently the latter will contain suflieient oxygen, in theform of aim-without employing any additional oxygen. If additionaloxygen is needed, it

I may be added to the hydrocarbon material prior to the alumina in thebauxite. contact between caustic and bauxite is less than about oneadsorbent treatment, or introduced directly into the treating zone.

The sweetened gasoline product removed from zone 12 has aconsiderablylower mercaptan content than the original sour gasoline.- Ithas been found'for example that a doctor sweet product or a producthaving mercaptan content of as measured by the amount of a standardaqueous solution containing copper ions which reacts with the gasolineproduct, can be obtained.

In place of ammonium hydroxide, gaseous ammonia can be used in thetreatment of the adsorbent prior to its use in sweetening.

- -Referring to Figure 2, thermally activated granular bauxitecontaining for example about 15 weight percent of. iron compounds as R0, is introduced into a magnetic separation zone 20 wherein a process,as well known inthe art, for magnetically separating bauxite particleshaving high-iron content from bauxite particles having .lower ironcontent is performed. The high iron bauxite,

containing for example about 50 weight percent of iron compounds as Fe 0is introduced into caustic treatment zone 21 wherein the bauxite iscontacted with caustic soda under conditions producing a substantialimprovement in the sweetening ability of the high iron bauxite withoutdestroying the essential granular structure or mechanical strength ofthe bauxite. In the light ,of thev present specification, suchconditions can readily be chosen by a person skilled in the art. Thestrength and. amount of caustic employed and the temperature .and timeof the treatment are factors for which, because of theirinterdependence, absolute limits cannot be set. Preferably, the amountof caustic used is less than the 'stoichiometric amount for reactionwith the alumina of .the bauxite; more preferably, the amount of causticemployed is about 0.5 to 2 moles of caustic per mole of Also,preferably, the time of hour.

Following the caustic treatment, the excess sodium hydroxide is removedfrom the bauxite, e.g. by washing with water until the pH of theeflluent wash water is mg with 20 cc. of distilled water, and then witha 28% (as NH solution of ammonium hydroxide in water until the efiluentliquid was free of precipitate, and removing eXcess water by heating at250-400 F. and 1 mm. Hg for 3 hours. In run No. 6, the treating agenthad been prepared by gently boiling for about 15 minutes a mixture of130 cc. of a magnetically separated high iron bauxite containing of ironcompounds as Fe O with 10 grams of sodium hydroxide and 200 cc. ofwater, washing the bauxite with water until the pH of the efiluent wasabout 7, and heating at 300-400 F. and 1 mm. Hg for 3 hours.

Run No. 1 is a comparison run for run No. 2, the ammonia treatmenthaving been omitted and the bauxite heated at 300400 F. and 1 mm. Hg.Run No. 3 is a. comparison run for run No. 4, the ammonia, ferricchloride, and ammonium hydroxide treatment having been omitted and thebauxite heated at BOO-400 F. and 1 mm. Hg. Run No. 5 is a comparison runfor run No. 6, the sodium hydroxide treatment having been omitted andthe bauxite bed were collected, the usual size of sample being 4000 cc.In each run, the amount of bauxite in the bed 'was cc. or 64 cc. 'Thevarious efilue'nt samples were tested for mercaptan content by titratingwith a standard aqueous solution containing copper ions. In each run,the amount of effluent collected before the percent mercaptan sulfur ofthe'efiluent substantially exceeded 0.0001 percent, was determined. Thisamount indicated the capacity of the bauxite for producing gasolinehaving mercaptan content not exceeding 0.0001 percent. The followingtable shows the results obtained:

Run N0. Gasoline Initial RSH, Bauxite Capacity,

Percent 1 cc.

Straight run, undried--- 0. 0034 Ordinary, untreated; 8,000 do 0. 0030Ordinary, NH; treated. 16, 000 Straight run, dried 0. 0027 Ordinary,untreated 28,000 0. 0020-0. 0035 Ordinary, Fe and N H; treated 64, 000Thermal, undried 0. 0012 High iron, untreated- 16,000 do '0. 0007-0.0010 High iron, NaOH, treated 44, 000

less than 8 and preferably about 7. Excess water is then removed, inzone 22 asindicated in Figure 2. The

Example I A series of runs was carried out wherein sour gasolines weresweetened by percolation in liquid phase at room 5 temperature throughbeds of bauxite. In run No. 2, the bauxite treating agent had beenprepared by saturating a .fresh commercial granular ignited bauxite(containing about 15% iron compounds as Fe O with gaseous ammonia andremoving excess ammonia by heating the .bauxite at 250-450 F. under anabsolute pressure of about 1 mm. Hg for two hours. In run No. 4, thetreatingagent had been prepared according to the procedure of run No. 2followed by saturating the. bauxite with The superiority of run 3 to run1 is probably attributable to the drying of the charge gasoline. In runNo. 6, the mercaptan content of the 'gasoline charge was about 0.0010%for the first 20,000 cc. charged, about 0.0009% for the next 12,000 cc.,and about 0.0007 for the next 12,000 cc. The superiority of run 6 to run5 is clear, in spite of the somewhat lower initial mercaptan content inrun 6. v

In runs 1, .2, 3 and 6, the space rate was about 5 volumes of gasoline.per volume of bauxite per hour throughout the run. In run 5, the spacerate was 8 for 5 the first 4000 cc. charged and 5.5 for the next 12,000cc.

charged. In run 4, thespace rate was 9 for the first 52,000cc. chargedand 5 for the next 12,000 cc. charged. The mercaptan content of theefiluent rose gradually to 0.0006% during the use of the 9 space rateand then dropped to an amount equal to or less than 0.000l% when thespace rate was reduced to 5. When the run was'terminated at 64,000 cc.of efiiuent, the mercaptan content of the lastkeflluent sample did notexceed 0.0001%. .This indicates that at space rate of 5, the

an about 60% solution of ferric chloride in water, wash- 75. bauxite ofrun 4 would have had a capacity of at least 64,000 cc., and thereforethe figure of 64,000 cc. is reported in the table.

This example shows. that. ammonia or sodium hydroxide treatment of freshbauxite containing iron compounds increases 'the ability of the bauxiteto reducethe mercaptan content of straight-- run or thermal gasoline.Other experiments haveshown that alkali-treated bauxite is alsoeffective in reducing the mercaptan content of catalytically crackedgasoline. Thus, in a run (No. '7) generally similar to run- 6 butemploying'catalytic gasoline as'charge and a more severe alkalitreatment (SO' grams of sodium hydroxide-and 150- cc. of water per 130cc. of bauxite), a capacity of 24,000'cc. at space rate of was obtained.

Example-II After 72,100 cc. of thermal gasoline had been percolatedthrough the bauxite in run 6 of Example I, the mercaptan content of theefliuent having risen to 0.0003- 0.0004% by that time, the flow ofgasoline was ceased, and steam was passed through the bauxite bed for 7hours. The bauxite was then heated at 400-500 F. and 1 mm. Hg for 3hours, followed by wetting with naphtha. Then the flow of thermalgasoline, this time having initial mercaptan content of 0.0011%, wasresumed at space rate of 5. The space rate was lowered to 3 after 32,000cc. of effluent had been collected. The capacity of thesteam-regenerated bauxite was found to be 36,000 cc., i.e. that much ofefiiuent was collected before the cercaptan content of the efl iuentsubstantially exceeded 0.0001 percent.

This example shows that a caustic-treated high iron bauxite (60 cc.)having 44,000 cc. capacity for thermal gasoline at space rate 5 can beregenerated with steam to produce a regenerated bauxite having 36,000cc. capacity for thermal gasoline at an average space rate ofapproximately 5.

Example III After 32,100 cc. of catalytic 'gasoline had been percolatedthrough the bauxite in run 7 of Example I, the mercaptan content of theeffluent having risen to 0.0003% by that time, the flow of gasoline wasceased, and steam was passed through the bauxite bed for one hour. Then200 cc. of 10% caustic soda were percolated through the bed at roomtemperature. Following this, the bed was filled with 10% caustic sodaand heated at steam temperature for one hour. Then the bed was drainedand water washed at steam temperature until the pH of the efiiuent waterwas about 7. The bauxite was then heated at 460 F. and 1 mm. Hg for 3hours. The flow of catalytic gasoline, now having initial mercaptancontent of 0.0009-0.0010% was resumed. The capacity of thecaustic-regenerated bauxite was found to be 12,000 cc.

This example shows that a caustic-treated high iron bauxite (60 cc.)having 24,000 cc. capacity for catalytic gasoline at space rate 5 can beregenerated with caustic to produce a regenerated bauxite having 12,000cc. capacity for catalytic gasoline at space rate 5.

Bauxite is a preferred adsorbent for use according to the invention, butother adsorbents can also be suitably employed. Any of the well-knownadsorbents for treatment of mineral oil fractions can be employed, e.g.fullers earth, silica gel, Attapulgus clay, Filtrol clay, infusorialearth, etc. If the adsorbent employed does not initially containsubstantial amounts of iron, for example 1% or more, iron should beadded to the adsorbent prior to the ammonium treatment according to theinvention. A particularly advantageous adsorbent is a magneticallyseparated bauxite containing about 10 to 70 weight percent, morepreferably 30 to 60 weight percent, of iron compounds as Fe O Anadsorbent which is used according to the invention can be one which hasbeen ignited or calcined prior to treatment with an alkali, or one whichhas not been ignited or calcined.

Temperatures ordinarily employed in igniting or calcining are those inthe approximate range from 600 F. to 1400" F. 1 p

The process of. the invention is particularly advan tageously appliedtogasoline fractionscontaining' mercaptans, but other petroleumfractions can alsobe treated for reduction of mercaptan content,v forexample spirits, naphtha', kerosene, etc. Preferably, a petroleumfraction treated according to the invention has not been acid treateddirectly prior, or remotely prior, to the adsorbent treatment. Straightrun or cracked petroleum fractions can be treated. However the yield oflow-mercaptan products obtainable with straight run fractions issubstantially greater than that obtainable with cracked fractions. It isbelievedthat, in-the-' case of cracked frac'tions,.these materialscontain constituents such as phenols, etc. which become adsorbed on theadsorbent and interfere with the reduction of mercaptan content.

The process of the invention involves in some embodiments contactinghydrocarbons with an adsorbent prepared by contacting a freshiron-containing adsorbent with an alkali; a fresh adsorbent being onewhich has not previously been used to reduce the mercaptan content ofhydrocarbon materials. Preferably, excess alkali is removed from thealkali-treated adsorbent prior to use of the latter to treathydrocarbons. However, in some cases this may not be necessary.

In copending application Serial No. 480,296, filed Jan uary 6, 1955, bythe present inventors, a method for reducing the mercaptan content ofmineral oil is disclosed and claimed, such method comprising contactingmineral oil containing mercaptans in liquid phase with magneticallyseparated bauxite containing about 20 to 70 weight percent of ironcompounds as Fe O The invention claimed is:

1. Process for reducing the mercaptan content of hydrocarbons whichcomprises contacting hydrocarbons containing mercaptans in liquid phasein the presence of oxygen with a porous solid adsorbent treating agentwhich has previously been exposed to temperature not exceeding 1400 F.,said treating agent having been prepared by contacting a porous solidadsorbent material containing iron compounds with an alkali and removingexcess alkali and any excess moisture from the adsorbent by procedurecomprising heating to a temperature above the volatilization temperatureof water under the prevailing conditions but not substantially above 600F., said treating agent containing combined water remaining after saidheating.

2. Process according to claim 1 wherein said adsorbent is bauxite.

3. Process according to claim 2 wherein said adsorbent is magneticallyseparated bauxite containing about 10 to 70 Weight percent of iron as F0 4. Process according to claim 1 wherein said alkali is an alkali metalhydroxide.

5. Process according to claim 4 wherein said removing is accomplished bywashing the adsorbent with water until the pH of the effluent water isbelow 8.

6. Process according to claim 1 wherein the alkali is aqueous sodiumhydroxide.

7. Process according to claim 6 wherein the amount of alkali employed isabout 0.5 to 2 moles of alkali per mole of alumina in the bauxite.

8. Process according to claim 1 wherein said alkali is ammonia.

9. Process according to claim 1 wherein the adsorbent has been contactedwith an aqueous solution of an iron compound prior to contacting withalkali.

10. Process according to claim 1 wherein the firstnamed contacting iseffected at approximately atmospheric temperature.

11. Process according to claim 1 wherein said treating agent is preparedby saturating fresh granular bauxite 13. Process according to claim 1wherein said hydrocarbons are straight run gasoline.

- 14. Process according to claim 1 wherein said hydrocarbons are crackedgasoline. f

15. Process according to claim 1 wherein said treating agent contains 1to 25 weight percent of iron.

References Cited the file of this patent UNITED STATES PATENTS -.Hood eta1 June 28, 1910 Richter June 2, 1914 Phillips et al Oct. 16, 1928Morrell et a1. May 8, 1934 Hoover May 26, 1936 Dolbear Apr. 18, 1939Kolthofi et al July 29, 1941 Thomas June 22, 1943 La Landc Aug. 10, 1943Frey June 5,1945 Agren June 24, 1947

1. PROCESS FOR REDUCING THE MERCAPTAN CONTENT OF HYDROCARBONS WHICHCOMPRISES CONTACTING HYDROCARBONS CONTAINING MERCAPTANS IN LIQUID PHASEIN THE PRESENCE OF OXYGEN WITH A POROUS SOLID ADSORBENT TREATING AGENTWHICH 1400*F., SAID TREATING HAVING BEEN PREPARED BY CONTACTING A POROUSSOLID ADSORBENT MATERIAL CONTAINING IRON COMPOUNDS WITH AN ALKALI ANDREMOVING EXCESS ALKALI AND ANY EXCESS MOISTURE FROM THE ADSORBENT BYPROCEDURE COMPRISING HEATING TO A TEMPERATURE ABOVE THE VOLATILIZATIONTEMPERATURE OF WATER UNDER THE PREVAILING CONDITIONS BUT NOTSUBSTANTIALLY ABOVE 600*F., SAID TREATING AGENT CONTAINING COMBINEDWATER REMAINING AFTER SAID HEATING.